A Study to Evaluate VIB7734 in Participants With Systemic Lupus Erythematosus (SLE), Cutaneous Lupus Erythematosus (CLE), Sjogren's Syndrome, Systemic Sclerosis, Polymyositis, and Dermatomyositis

This study will have 3 periods: screening, treatment period, and extended follow-up. The screening period is 28 days. A total of 32 participants will be enrolled in 3 cohorts with 8 participants in Cohort 1, and 12 participants each in Cohorts 2 and 3. In Cohort 1, participants will be randomized in a 3:1 ratio to receive VIB7734 or matching placebo by injection every 4 weeks (q4w) for a total of 3 doses on Days 1, 29, and 57. In Cohorts 2 and 3, participants diagnosed with lupus only will be randomized in a 2:1 ratio to receive VIB7734 or matching placebo by injection q4w for 3 doses on Days 1, 29, and 57. Participants will be followed until at least Day 141. After the Day 141 visit, participants will exit the study if participants meets adequate plasmacytoid dendritic cells (pDCs). If an adequate pDC level does not meet at Day 141 visit, the participant will continue the follow-up for pDC repletion until they meet the protocol defined adequate pDC level or Day 337 visit has been reached. Study acquired from Horizon in 2024. Originally Viela Bio was the sponsor.